welcome and congratulations on your purchase
the "P" is for radio Program ... that is, the [STORE] is taking the current tuning frequency (MW, LW, or FM) and wanting to now assign a number to it so you can recall it
Do you have one of the two controls that supports the Beomaster ?
Either the Terminal 5000 or the Master Control Panel 5000 ?
I strongly recommend you take up a Gold membership to Beoworld ... you will be automatically registered in the monthly raffle ... and you will also have access to scanned copies of the manuals in the Product section of the Beoworld site
First B&O (1976) was a Beogram 1500 ... latest (2011) change has been to couple the BL11 with the BL6Ks *sounds superb*